The original publication is available at http://journals.plos.org/plosone/

Publication of this article was funded by the Stellenbosch University Open Access Fund.

Article

Pseudomonas aeruginosa and Staphylococcus aureus are commonly associated with hospital-
acquired infections and are known to form biofilms. Ciprofloxacin (CIP), which is normally
used to treat these infections, is seldom effective in killing cells in a biofilm. This is
mostly due to slow or weak penetration of CIP to the core of biofilms. The problem is accentuated
by the release of CIP below MIC (minimal inhibitory concentration) levels following a
rapid (burst) release. The aim of this study was to develop a drug carrier that would keep
CIP above MIC levels for an extended period. Ciprofloxacin was suspended into poly(D,Llactide)
(PDLLA) and poly(ethylene oxide) (PEO), and electrospun into nanofibers (CIP-F).
All of the CIP was released from the nanofibers within 2 h, which is typical of a burst release.
However, 99% of P. aeruginosa PA01 cells and 91% of S. aureus Xen 30 cells (a methicillinresistant
strain) in biofilms were killed when exposed to CIP-F. CIP levels remained above
MIC for 5 days, as shown by growth inhibition of the cells in vitro. The nanofibers were
smooth in texture with no bead formation, as revealed by scanning electron and atomic
force microscopy. A single vibration peak at 1632 cm-1, recorded with Fourier transform infrared
spectroscopy, indicated that CIP remained in crystal form when incorporated into
PDLLA: PEO. No abnormalities in the histology of MCF-12A breast epithelial cells were observed
when exposed to CIP-F. This is the first report of the inhibition of biofilm formation by
CIP released from PDLLA: PEO nanofibers.